This invention relates to antenna systems and more particularly to phased array antenna systems.
As is known in the art, an array antenna includes a plurality of individually radiating elements. In some systems the individual radiating elements are coupled to a transmitter through a transmitter element for controlling the phase and amplitude of the transmitted signal. Similarly, the individual radiating elements are coupled to a receiver through a receiver element, for controlling the phase and amplitude of the received signal. In other systems the individual radiating elements are coupled to both the transmitter and receiver through a single element here referred to as a transceiver for controlling the phase and amplitude of both transmitted and received signals. The relative phase and amplitude of the microwave frequency signal passing between the plurality of radiating elements and a corresponding plurality of individual transceiver elements are controlled to obtain a desired radiation pattern. The pattern obtained is a result of the combined action of all the individual transceiver and radiating elements. Many devices such as ferrite phase shifters are used to control the phase of the microwave frequency signal. Many of such phase shifters are reciprocal, that is, the phase shift of a signal passing through one of such devices is independent of the direction which the signal passes through. In some applications it is desirable to provide an active phase shifter to provide gain to a signal passing there through. Such a phase shifter is generally inherently nonreciprocal. Thus, the use of an nonreciprocal phase shifter in a transceiver would require the use of two of such phase shifters. A developing trend in phased array antenna systems is toward production of the transceiver elements in monolithic integrated circuit form. This is desired in order to reduce cost and size factors generally associated with phased array antenna systems and to provide phased array antennas adapted for certain applications where size and cost are critical such as airborne or spaced based radar systems.